Abstract
The purpose is to elucidate the effects of the duration of heat treatment on the resistance of vegetable oils to oxidative processes. Iodine and acid values were analyzed before and after heat exposure. Rapeseed oil, sunflower oil, and a blend of rapeseed and sunflower oils (ratio 55:45) were used as samples. Sunflower oil heated at a temperature of 40°C for 80 minutes had its peroxide value increased by 3.0 times (p ≤ 0.05) as compared to rapeseed oil and the blend. At 75°C, the peroxide value increased by 4.0 times for sunflower oil (p ≤ 0.05), by 3.0 and 3.3 times for rapeseed oil (p ≤ 0.05), and by 3.1 and 3.4 times for the blend (p ≤ 0.05). At 40°C, no peroxide values were obtained that exceeded the threshold limits. The concentration of fatty acids in oils depends on the plant variety, growth conditions and maturity of seeds or fruits. Therefore, the concentration of fatty acids in the oil should be measured before oil blending.